The invention relates to an endoscope, in particular a flexible video endoscope, having a shaft which, at its distal end, terminates in an endoscope head having at least one light inlet and at least one channel for passage of a flushing medium, and with a deflecting element which is arranged at a distance in front of a mouth of the channel in order to deflect the emerging flushing medium to the light inlet.
An endoscope of this kind is known from U.S. Pat. No. 4,436,087, for example.
Endoscopes of this kind are used in particular for viewing hollow organs within the body. With flexible endoscopes, it is possible, for example, to examine the trachea, the oesophagus, the stomach or the intestine.
At the distal end, a light inlet is provided through which the light of the image to be observed is introduced and then conveyed to the proximal end. In rigid endoscopes, this is done using a rod lens system; in modern flexible endoscopes, a light-sensitive chip, arranged in the distal endoscope head, converts the incoming light signals into an electrical signal and conveys this to the proximal head section. There, the electrical signal is converted again into an image signal and, for example, displayed on a monitor.
In practical application, it has now been found that the light inlet or image inlet becomes soiled and that it is necessary to clear it of contaminating material.
For this purpose, it has been proposed to provide a channel running through the shaft of the endoscope for the passage of a flushing medium, for example a gaseous or a liquid medium. Since this channel by necessity has to run alongside the optics channel, suitable measures have to be taken to deflect the flushing medium sideward and guide it across the light inlet in order to clean the latter. Numerous construction proposals have now been made for how this jet of flushing medium can be deflected.
In the aforementioned U.S. Pat. No. 4,436,087, this is achieved by a cap being fitted, in most cases screwed, onto the distal end of the endoscope head, with a deflecting element projecting radially inwards from the inner side of said cap.
In this case, the deflecting element is configured such that it comes to lie at a slight distance in front of the mouth of the channel from which the flushing medium emerges. The emerging flushing medium then hits the deflecting element, is diverted sideward by the latter from the axial direction to a radial direction, and the jet of flushing medium is guided across the light inlet in order to flush or blow it clear.
Certain disadvantages of this construction have been found in practical application.
The inner cavity of the cap proved to be a kind of dirt trap and tends to cause more soiling of the light inlet than is the case in an endoscope without such a cap.
To clean a flushing channel, for example by a cleaning brush being guided through it in the axial direction, the cap has to be taken off, since otherwise the brush would strike against the deflecting element. Bearing in mind that endoscopes have a diameter in the range of a few millimeters, it is evident that the components involved here are relatively small and sensitive.
A further disadvantage is that the fitted closure cap finally has to be positioned very exactly with respect to the deflecting element to ensure that the desired deflection result can be achieved.
It is customary for several channels to be routed through the shaft of an endoscope, that is to say not just the channel for the optics and a flushing channel, but in most cases also one or more channels for guiding the illumination light, and often also an instrument channel for guiding an instrument through the shaft.
To allow the light inlet to be flushed clear or blown clear in the desired manner, the deflecting element then has to come to lie in a very specific position over the mouth of the flushing channel so that the jet is in fact guided across the light inlet and not across the instrument channel. At the same time, the deflecting element has to be so small that it does not impede the entry of light into the light inlet and does not screen off the illumination light or even block the instrument channel. That is to say, the deflecting element projects from an inner circumferential face of the cap within a relatively small area.
If the cap is now screwed on too little or too far, the deflecting element does not come to lie in its exactly predetermined position, and the desired flushing result is not achieved.
From U.S. Pat. No. 5,746,695 an endoscope of the above mentioned kind is known having a closing cap comprising the deflecting element as an integral part for deflecting the emerging flushing medium laterally towards the light inlet. Contrary to the above mentioned construction with a cap which can be screwed on, the cap is contoured in a manner that it can be placed only in a particular orientation on the distal end of the endoscope. For it, both the distal end of the endoscope head and the cap are provided with respective complementary projections and recesses respectively for assuring a correct positioning of the cap together with the deflecting element.
The disadvantage of that construction is that both the distal end of the endoscope head and the corresponding face of the cap are designed very complicated. This needs an expensive machining of these parts. Further, the numerous recesses and undercuts provide bacteria niches and therefore need very deep cleaning and sterilization processes.
It is an object of the present invention to provide simple construction measures that guarantee an exact positioning of the deflecting element so that it is possible to achieve an exactly oriented jet of flushing medium even after several dismantling, cleaning and assembling procedures.